Flower-like Ag2WO4/CeO2 heterojunctions with oxygen vacancies and expedited charge carrier separation boost the photocatalytic degradation of dyes and drugs.

Charge carrier separation is a very important factor in photocatalysis, and it may be achieved through a variety of paths including the construction of heterojunctions and the formation of surface defects. Herein, we demonstrate the construction of flower-like Ag2WO4/CeO2 heterojunctions (namely ACs) by in situ deposition of Ag2WO4 on the surface of flower-like CeO2 with oxygen defects. The ACs with 2.3%, 3.8%, and 5.3% Ag2WO4 are defined as AC-1, AC-2, and AC-3, respectively, and we compare their photocatalytic removal efficiencies. Under visible light, AC-2 exhibits the highest photocatalytic removal efficiency toward cationic dye RhB and tetracycline (TC). The K value of AC-2 toward RhB degradation is determined to be 0.059 min-1, which is 7.56 and 8.94-fold higher than those of Ag2WO4 (0.0078 min-1) and CeO2 (0.0066 min-1), respectively. Moreover, the K value of AC-2 toward TC degradation (0.021 min-1) is 4.04 and 5.68-fold higher than those of Ag2WO4 (0.0052 min-1) and CeO2 (0.0037 min-1), respectively. Our results clearly demonstrate that the introduction of Ag2WO4 particles stimulates the formation of surface defects of CeO2, improves the visible light absorption, accelerates the charge carrier separation, and consequently boosts the photocatalytic degradation of dyes and drugs.

Estimation of Nuclear Medicine Exposure Measures Based on Intelligent Computer Processing.

This paper provides an in-depth discussion and analysis of the estimation of nuclear medicine exposure measurements using computerized intelligent processing. The focus is on the study of energy extraction algorithms to obtain a high energy resolution with the lowest possible ADC sampling rate and thus reduce the amount of data. This paper focuses on the direct pulse peak extraction algorithm, polynomial curve fitting algorithm, double exponential function curve fitting algorithm, and pulse area calculation algorithm. The detector output waveforms are obtained with an oscilloscope, and the analysis module is designed in MATLAB. Based on these algorithms, the data obtained from six different lower sampling rates are analyzed and compared with the results of the high sampling rate direct pulse peak extraction algorithm and the pulse area calculation algorithm, respectively. The correctness of the compartment model was checked, and the results were found to be realistic and reliable, which can be used for the analysis of internal exposure data in radiation occupational health management, estimation of internal exposure dose for nuclear emergency groups, and estimation of accidental internal exposure dose. The results of the compartment model of the respiratory tract and the compartment model of the digestive tract can be used to calculate the distribution and retention patterns of radionuclides and their compounds in the body, which can be used to assess the damage of radionuclide internal contamination and guide the implementation of medical treatment.

Metal-Free B, N co-Doped Hierarchical Porous Carbon Electrocatalyst with an Excellent O2 Reduction Performance.

Fuel cells have attracted increasing attention due to their low cost, high energy density, low environmental pollution, and abundant raw materials. Oxygen reduction reaction (ORR) is a core technology of fuel cells, and the development of new electrocatalysts with high ORR performance is highly desirable. Herein, we synthesize a series of B, N co-doped hierarchical porous carbons using a soft template method with the integration of self-assembly, calcination and etching. The obtained materials exhibit hierarchical porous structures, controllable pore distribution, partial graphite structures, and B, N co-doping. They can function as the cost-effective and metal-free electrocatalysts, facilitating the diffusion of electrolyte ions and the improvement of ORR performance. Especially, the B, N co-doped porous carbon with the B-to-N molar ratio of 5 (BNC-5) displays a high ORR activity with a half-wave potential (E1/2 ) of 0.73 V, an onset potential (Eonset ) of 0.94 V, and a high limiting current density (JL ) of 5.98 mA cm-2 , superior to the N-doped C (NC) and BNC-1 (the B-to-N molar ratio=1), BNC-3 (the B-to-N molar ratio=3) and BNC-7 (the B-to-N molar ratio=7) under the identical conditions. Moreover, the BNC-5 exhibits good cycling stability after 5000 cyclic voltammetry (CV) cycles and excellent tolerance toward even 3 M methanol. This research provides a new approach for the facile synthesis of dual element-doped carbon electrocatalysts with high ORR performance.

Construction of 2D/2D layered g-C3N4/Bi12O17Cl2 hybrid material with matched energy band structure and its improved photocatalytic performance.

A series of visible-light-induced 2D/2D layered g-C3N4/Bi12O17Cl2 composite photocatalysts were successfully synthesized by a one step chemical precipitation method with g-C3N4, BiCl3 and NaOH as the precursors at room temperature and characterized through XRD, FTIR, XPS, TEM, BET and UV-vis DRS measurements. The results of XRD, FTIR and XPS indicated that g-C3N4 has been introduced in the Bi12O17Cl2 system. The TEM image demonstrated that there was strong surface-to-surface contact between 2D g-C3N4 layers and Bi12O17Cl2 nanosheets, which contributed to a fast transfer of the interfacial electrons, leading to a high separation rate of photoinduced charge carriers in the g-C3N4/Bi12O17Cl2 system. Rhodamine B was considered as the model pollutant to investigate the photocatalytic activity of the resultant samples. The g-C3N4/Bi12O17Cl2 composite showed a clearly improved photocatalytic degradation capacity compared to bare g-C3N4 and Bi12O17Cl2, which was ascribed to the interfacial contact between the 2D g-C3N4 layers and Bi12O17Cl2 sheet with a matched energy band structure, promoting the photoinduced charges' efficient separation. Finally, combined with the results of the trapping experiment, ESR measurements and the band energy analysis, a reasonable photocatalytic mechanism over the 2D/2D layered g-C3N4/Bi12O17Cl2 composite was proposed.

Novel synthesis of magnetic, porous C/ZnFe2O4 photocatalyst with enhanced activity under visible light based on the Fenton-like reaction.

Magnetic visible-light-driven photocatalyst, porous C/ZnFe2O4 (denoted as C/ZFO-CE) was fabricated via a CO2-mediated ethanol route. CO2-mediated ethanol route largely mitigated the solvent strength and facilitated the homogenous deposition of ZnFe2O4 (ZFO) through the coordination of metallic cation with CO32- and HCO3- anions, which were hydrolyzed from CO2 and H2O, thereby avoiding additional precipitant. Moreover, the HCO3-, CO32- and NO3- in the system acted as templates for the formation of porous C avoiding the additional organic mesoporous templates, thus reducing the synthesis cost. For the degradation of RhB and phenol, the C/ZFO-CE system in presence of minute H2O2 exhibited remarkably improved catalytic performance compared with the systems of H2O2, ZFO, C/ZFO-CE, C/ZFO-E (C/ZnFe2O4 synthesized in pure ethanol) and C/ZFO-E in the presence of minute H2O2. Furthermore, 2.0 mL of H2O2 (30%) combined with C/ZFO-CE obtained the maximum degradation efficiencies of 100% for RhB within 60 min and 91% for phenol within 120 min. The high efficiency for degradation of pollutants over C/ZFO-CE catalyst in the presence of minute H2O2 was possibly attributed to the strong harvest of visible light, the improved separation efficiency of the photoinduced charges and the overall ˙OH production by the "photo-Fenton" process. The existence of ˙OH during photodegradation process was evidenced via the PL-TA (photoluminescence-terephthalic acid) technique, ESR spectra and trapping experiments of active species using different scavengers. Furthermore, a possible reaction mechanism involving the Fenton-like reaction for the photodegradation of pollutants is proposed based on the experimental results.

Periodic Mesoporous Organosilica with a Basic Urea-Derived Framework for Enhanced Carbon Dioxide Capture and Conversion Under Mild Conditions.

A periodic mesoporous organosilica with a basic urea-derived framework (PMO-UDF) was prepared and characterized thoroughly. The PMO-UDF showed an enhanced CO2 capture capacity at low pressure (≤1 atm) and an exceptional catalytic activity in CO2 coupling reactions with various epoxides to yield the corresponding cyclic carbonates under mild conditions because of the presence of a high surface area, basic pyridine units, and multiple hydrogen-bond donors. The highly stable catalyst could be reused at least six successive times without a significant decrease of the catalytic efficiency or structural deterioration, thus the PMO-UDF composite is considered as a promising material for CO2 capture and conversion.

Ag2CrO4 nanoparticles loaded on two-dimensional large surface area graphite-like carbon nitride sheets: simple synthesis and excellent photocatalytic performance.

Graphite-like carbon nitride (g-C3N4) with a large surface area was prepared through thermal condensation of guanidine hydrochloride at 650 °C. Various amounts of silver chromate (Ag2CrO4) nanoparticles with small size were highly loaded on the g-C3N4 by a simple co-precipitation method at room temperature. The chemical constituents, surface structure and optical properties of the resultant Ag2CrO4/g-C3N4 composites were thoroughly characterized. And the photocatalytic performances were evaluated by degradation of Rhodamine B (RhB) and phenol, the experimental results indicated that the as-prepared Ag2CrO4/g-C3N4 composites presented excellent photocatalytic activity under visible-light irradiation. With the mass ratio of Ag2CrO4 to g-C3N4 at 1 : 2, the Ag2CrO4/g-C3N4 composites exhibited optimal photocatalytic activity for degrading RhB, approximately 6.1 and 10.4 times higher than those on pure g-C3N4 and bare Ag2CrO4 particles. The improved photocatalytic activity was mainly attributed to the combined effect including the larger surface area, highly dispersed smaller Ag2CrO4 nanoparticles, stronger visible absorption and higher charge separation efficiency of the Ag2CrO4/g-C3N4 composites. Moreover, the possible mechanism for the photocatalytic activity was tentatively proposed.

A Simple Method for the Preparation of TiO2 /Ag-AgCl@Polypyrrole Composite and Its Enhanced Visible-Light Photocatalytic Activity.

A novel and facile method was developed to prepare a visible-light driven TiO2 /Ag-AgCl@polypyrrole (PPy) photocatalyst with Ag-AgCl nanoparticles supported on TiO2 nanofibers and covered by a thin PPy shell. During the synthesis, the PPy shell and Ag-AgCl nanoparticles were prepared simultaneously onto TiO2 nanofibers, which simplified the preparation procedure. In addition, because Ag-AgCl aggregates were fabricated via partly etching the Ag nanoparticles, their size was well controlled at the nanoscale, which was beneficial for improvement of the contact surface area. Compared with reference photocatalysts, the TiO2 /Ag-AgCl@PPy composite exhibited an enhanced photodegradation activity towards rhodamine B under visible-light irradiation. The superior photocatalytic property originated from synergistic effects between TiO2 nanofibers, Ag-AgCl nanoparticles and the PPy shell. Furthermore, the TiO2 /Ag-AgCl@PPy composite could be easily separated and recycled without obvious reduction in activity.

Insights into hydrogen bond donor promoted fixation of carbon dioxide with epoxides catalyzed by ionic liquids.

Catalytic coupling of carbon dioxide with epoxides to obtain cyclic carbonates is an important reaction that has been receiving renewed interest. In this contribution, the cycloaddition reaction in the presence of various hydrogen bond donors (HBDs) catalyzed by hydroxyl/carboxyl task-specific ionic liquids (ILs) is studied in detail. It was found that the activity of ILs could be significantly enhanced in the presence of ethylene glycol (EG), and EG/HEBimBr were the most efficient catalysts for the CO2 cycloaddition to propylene oxide. Moreover, the binary catalysts were also efficiently versatile for the CO2 cycloaddition to less active epoxides such as styrene oxide and cyclohexene oxide. Besides, the minimum energy paths for this hydrogen bond-promoted catalytic reaction were calculated using the density functional theory (DFT) method. The DFT results suggested that the ring-closing reaction was the rate-determining step in the HEBimBr-catalyzed cycloaddition reaction but the EG addition could remarkably reduce its energy barrier as the formation of a hydrogen bond between EG and the oxygen atom of epoxides led this process along the standard SN2 mechanism. As a result, the ring-opening reaction became the rate-determining step in the EG/HEBimBr-catalyzed cycloaddition reaction. The work reported herein helped the understanding and design of catalysts for efficient fixation of CO2 to epoxides via hydrogen bond activation.

A Facile and One-Step Synthesis of Visible-Light-Responsive Silver and Mesoporous Carbon Comodified Carbon-Zinc Oxide Composites.

Silver and mesoporous carbon (mC) comodified CZnO composites (Ag/mC/CZnO) were fabricated by a facile, one-step process directly from C, Ag, and Zn precursors in CO2 -expanded ethanol, which provided a unique medium and did not require additional precipitant and mesoscaled organic templates. When the composite photocatalyst was applied to the degradation of rhodamine B and phenol, Ag/mC/CZnO exhibited excellent photocatalytic activity in visible light. The remarkably improved catalytic activity of the composites was attributed to the following synergistic effects. The modification of mC enriched the adsorption of pollutants on the photocatalyst. Additionally, the mesopores of carbon provided a spacious path for the separation of photogenerated electrons and holes. In addition to mC, carbon was also doped into ZnO, which narrowed the ZnO band gap. The modification of silver strengthened the absorbance of the visible region and improved the electron-trapping ability.

CO2-assisted synthesis of mesoporous carbon/C-doped ZnO composites for enhanced photocatalytic performance under visible light.

Visible-light-responsive mesoporous carbon/C-doped ZnO (mC/C-ZnO) composites were fabricated using a facile, fast, one-step process in CO2-expanded ethanol solution. It is a green and sustainable process that does not need tedious pretreatment, surfactants or precipitants. CO2 played triple roles in the synthesis of mC/C-ZnO composites; the first was to provide a simple physical expansion to evenly dope the carbon in the ZnO; the second was to offer some chemical groups such as CO3(2-) and HCO3(-), facilitating the uniform and complete deposition through the coordination of a metallic cation with these anions; and the third was to offer CO3(2-) acting as a template for the formation of mesoporosity in the carbon. When used as a photocatalyst for the photodegradation of RhB and the organic pollutant phenol, the mC/C-ZnO composites with glucose content at 22 wt% (mC/C-ZnO-CE-2) synthesized in CO2-expanded ethanol exhibited better recycling stability and photodegradation rate than the corresponding sample synthesized in pure ethanol. Such improved photocatalytic performance was attributed to the well-mixing of the mesoporous carbon and the small sized C-doped ZnO particles in the mC/C-ZnO-CE-2 composites. The facile and fast synthesis method could be extended to other mesoporous carbon/C-doped metal oxide composites, which are expected to be good photocatalyst candidates, or in other application fields.

Remarkably enhanced photocatalytic activity of ordered mesoporous carbon/g-C3N4 composite photocatalysts under visible light.

Ordered mesoporous carbon/g-C3N4 (OMC/g-C3N4) composites with efficient photocatalytic activity under visible light irradiation were prepared by a facile heating method. The as-prepared OMC/g-C3N4 composites were thoroughly characterized by X-ray diffraction, Fourier transform infrared spectroscopy, elemental analyses, transmission electron microscopy with energy dispersion X-ray spectroscopy, N2 adsorption-desorption analysis, UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The photocatalytic activities were evaluated by degrading Rhodamine B dye, and OMC/g-C3N4 composites exhibited much higher photocatalytic activities than pristine g-C3N4. Moreover, the catalysts retained good stability and the photodegradation efficiency hardly changed after five cycles. The degradation rate of the OMC/g-C3N4 photocatalyst was almost 10 times as high as that of the pristine g-C3N4, which indicated that OMC played an important role in the remarkable improvement of photocatalytic activity. The significant enhancement in photodegradation activity over the OMC/g-C3N4 catalyst could be ascribed to the combined effects coming from the enhanced visible light adsorption, enriched adsorption of the dye on the catalyst and subsequent efficient separation of photogenerated electrons and holes. In addition, a possible mechanism for the photodegradation process was proposed on the basis of active species scavenging experiments.